Surge protection necessary in 12V vehicles?

Hi all,

I am building a few circuits for LED lighting in a vehicle and was wondering if any sort of surge protection is required. On the Arduino side I have a LM7805 regulating down to 5V with 2 caps. The circuit I am tapping into is fused, but should I be doing anything to protect against voltage spikes? (eg startup?)

I'm no EE, but startup is more likely to produce dips than spikes, isn't it?

Good point... I guess in this day and age, new cars must have good regulation from the alternator/main controller components since so many peripherals are high tech and potentially more sensitive. I am wondering if maybe it is just a Cap across the input +/- to smooth things out, but not sure.

I haven’t actually checked with an oscilloscope or anything but I’ve done alot of thing with my cars 12/14 volts running, starting whatever and I haven’t seen any harmfuk side effects
definelty the caps on certain extra sensitive stuff, but that’s for anywhere

If you want to build something correctly that will last as long as anything else in your car, yes there is a lot protection needed. If this part of a Halloween prop or something you think you'll get board with and remove quickly than not really - but don't be sad if it gets killed.

A normally running car isn't that nasty of an environment (opinions vary on this, but for a one off not permanent project/prototype in a fairly modern car, this is how I feel), but there are many things that can go wrong and produce a surprising amount of havoc. Load dump is probably the nastiest, but other common ones are reverse polarity, 24v input (some of the jumper packs output 24v).

The LM2940 is basically a 7805 with some of the needed protection built in, but both of these may get quite hot and burn out/trip thermal protection with a medium sized load on them when dropping 7 - 9 volts.

Use a universal power adapter available from any electronics store. It will have the required surge protection and regulation built in.

I would suggest a 7812 to feed an arduino and then take the 5 volts off that,
But if the leds are just being switched on and off the car feed then I would not worry about it, unless its high power leds that need constant current
also if possible you can rewire the leds so that they are in series and need a higher voltage closer to 12 which would save you some heat trying to drop the voltage,
or find something like I did off ebay a 12/24 to 5v 3a buck converter where they already designed and is bug free

winner10920:
I would suggest a 7812 to feed an arduino and then take the 5 volts off that....

No can do.. I am using an ATTiny85 circuit with a 3.3V regulator (corrected from the 7805 above) to drive it, and then using the ATTiny to control MOSFETs to PWM the LED strips with 12V from the car. I am not so worried about the LEDs, but concerned about the 3.3 regulator into the ATTiny. As a FYI - I am using it to light LEDs (red) along with the tail lights (at 75%), but also ‘watch’ the brake application. When the brakes are applied the LEDs PWM to 100% giving the effect that they are part of the system.

The 7805, with input and output caps is your surge protection. No worries there, BUT,, An automobile is a very noisey (electrically) environment. be sure to use bypass filters (.1uF {100nF?}) from regulator out to ground close to the Arduino power input, and signal to ground on any long signal lines.